WO2002080276A1 - Production method for simox substrate and simox substrate - Google Patents

Abstract

A high-quality SOI substrate increased in BOX layer thickness and a production method therefor, in an SIMOX substrate produced by using a low-dose-region implanting amount as an oxygen ion implanting amount. A production method for an SIMOX substrate which implants oxygen ions into a silicon substrate and then heat treats it at high temperature to form a buried oxidized layer and a surface silicon layer, wherein after forming a buried oxidized layer by a high-temperature heat treating after oxygen ion implantation, the step of performing another oxygen ion implantation so that the maximum position of an implanted oxygen distribution is disposed below the interface between the buried oxidized layer formed by then and the substrate below that layer and then performing high-temperature heat treating is repeated; and an SIMOX substrate having a surface silicon layer thickness of at least 10 nm and up to 400 nm, and a buried oxidized layer thickness of at least 60 nm and up to 250 nm.

Description

 Specification

SIM0X substrate manufacturing method and SIM0X substrate

 The present invention relates to an S0I substrate in which a buried oxide layer is disposed near the surface of a silicon substrate, and a surface single-crystal silicon layer (hereinafter referred to as a SOI (Silicon-on-insulator) layer) is formed thereon. Background art

 As an S0I substrate on which a single-crystal silicon layer is formed on an insulator such as a silicon oxide, a SIMOX (Separation by IMplanted OXygen) substrate and a bonded wafer are mainly known. In the SIM0X wafer, oxygen ions are implanted into the single-crystal silicon substrate by ion implantation, and the oxygen ions and silicon atoms are chemically reacted by a subsequent annealing process to form a buried oxide layer (hereinafter referred to as BOX ( This is an S0I substrate obtained by forming a (buried oxide) layer). On the other hand, a bonded wafer is an S0I substrate obtained by bonding two single-crystal silicon wafers with an oxide layer interposed therebetween and thinning one of the two wafers.

The MOSFET (Metal-oxide-semiconductor field effect transisitor) formed on the S0I layer of the S0I substrate has high radiation qualities, latch-up resistance, and high reliability. Short-channel effects due to miniaturization of devices are suppressed, and low power consumption operation becomes possible. Also, since the device operation area is capacitively insulated from the substrate itself, the signal transmission speed is improved, and high-speed operation of the device can be realized. For these reasons, S0I substrates are used for next-generation M0S-LSIs. Is expected as a high-performance semiconductor substrate.

 Of these S0I substrates, SIM0X wafers have the feature of particularly excellent thickness uniformity of the S0I layer. On a SIM0X wafer, a SOI layer with a thickness of 0.4 μm or less can be formed as an SOI layer, and an S0I layer with a thickness of about Ο. Ϊ́μπι or less can be well controlled. In particular, an S0I layer with a thickness of 0.1 / zm or less is often applied to the formation of a fully depleted M0S-LSI, in which case the thickness of the S0I layer itself is proportional to the threshold voltage of the M0SFET operation. Therefore, the uniformity of the thickness of the S0I layer is an important quality for fabricating devices with uniform performance with high yield. From this point of view, SIM0X wafers with excellent S0I layer thickness uniformity are expected as substrates for next-generation M0SFETs.

 The M0S-LSI fabricated on the S0I substrate has a device formation area that is electrically insulated from the substrate body through the BOX layer, which is an insulator. Immunity: Excellent characteristics such as improved latch-up immunity, low power consumption operation, and ultra-high speed operation can be realized. Therefore, the BOX layer is required to have more complete electrical insulation. Specifically, it is required that the BOX layer has as few leak defects (hereinafter referred to as pinhole defects) as much as possible and has a breakdown voltage closer to that of the thermal oxide layer.

In the preparation of SIM0X substrate, usually a single acceleration energy, but the Scripture type manner Ru performed the injection of oxygen Ion using accelerating voltage of about 200 kV, in which case the amount of implantation of oxygen ions 1.5Xl0 ¹⁸ cm- or ^two or more regions, 2. δ δΧΐΟ ¹⁷ cnf only in no event either a limited area in the range of ^2, in SIM0X structure obtained after high temperature heat treatment, one or continuous uniform quality good BOX It is well known that layers can be obtained (eg, I. Nakashima and K. Izumi, Journal of Materials Research, Vol. 8, p. 523 (1993)). Using these oxygen ion implantation doses Conventionally, the SIMOX substrate fabricated using the former oxygen ion implantation region is a high dose SIM0X substrate, and the latter fabricated using the oxygen ion implantation region is a low dose SIM0X substrate. is called.

 The high-dose SIM0X substrate and the low-dose SIM0X substrate have their own characteristics, and they are used according to the characteristics. Of these, the low-dose SI M0X substrate is expected to be a technology that can reduce the threading dislocation density of the S0I layer and achieve low cost because the oxygen ion implantation amount is relatively small. . However, the low-dose SIM0X substrate had problems such as a high frequency of pinhole defects in the BOX layer and a high probability of insufficient insulation resistance of the BOX layer due to the thin BOX layer. Regarding these qualities of low-dose SIM0X substrates, if the BOX layer is made thicker by simply increasing the amount of implanted oxygen ions, pinhole defects are reduced, but particles inside the BOX layer are reduced. A large number of silicon-like inclusions (hereafter referred to as silicon islands) are generated, and as a result, the dielectric strength of the BOX layer is reduced. On the other hand, when the amount of implanted oxygen ions is reduced, the above-mentioned silicon-containing material is reduced and the dielectric strength of the BOX layer is improved, but the density of pinhole defects is increased as the amount of implanted oxygen ions is reduced. It has been pointed out that this will happen. Therefore, it has been extremely difficult to simultaneously improve the quality of these BOX layers on a low-dose SIM0X substrate according to the prior art.

As a technology that contributes to the improvement of the quality of the BOX layer of this low-dose SIM0X substrate, a technology using an internal thermal oxidation process (hereinafter, abbreviated as ITOX technology) at high temperatures has been proposed. Nakajima et al., JP-A-07-263538, Arima, S. Nakashima Horik, Journal of Electrochemical Society, Vol. 143, p. 244). Depends on ITOX technology For example, a thermal oxide layer grows on the substrate surface due to the oxidation treatment at a high temperature, and at the same time, a small amount of oxide film grows on the upper interface of the BOX layer, so that the BOX layer can be made thicker. As a result, it is reported that both reduction of pinhole defects and improvement of dielectric strength can be achieved. However, in the IT0X technology, it is necessary to grow the surface oxide layer more than 10 times the increment of the layer thickness in the BOX layer.Therefore, in order to secure a predetermined SOI layer in the finally obtained SIM0X structure, However, it was necessary to limit the amount of oxidation of the substrate surface, and as a result, the increase of the BOX layer was naturally limited.

As a method to increase the thickness of the BOX layer of the SI M0X substrate without being restricted by this limitation, a method of performing a series of oxygen ion implantation while changing the average implantation depth stepwise or continuously and then performing high-temperature heat treatment In the above, the injection oxygen distribution added and accumulated after a series of oxygen ion injections is controlled so as to be in a condition range where silicon islands do not occur, and a single BOX layer is formed after high-temperature heat treatment. It has been proposed to control the distribution so as to have a single peak (JP-A-7-201975). According to this method, a good BOX layer cannot be obtained when oxygen ion implantation is performed using a single accelerating voltage. Obtaining in principle is possible. However, in order to prevent the silicon island BOX layer is the peak value of the injection of oxygen distribution, oxygen concentration of the silicon oxide 4. is about half of the ^{48 X l0 2 2 cm- 3 2} . 25 X 10 ^{2 2} cm— ³ or less, but if multiple peaks occur in the implanted oxygen distribution after a series of oxygen ion implantation due to process condition fluctuations, etc., Precipitation occurs around each peak, and a single BOX layer cannot be obtained, which has instability.To avoid these, strict and delicate control is required. There was a problem. On the other hand, as a technique for repeating oxygen ion implantation and high-temperature heat treatment, a technique for repeating oxygen ion implantation with the same acceleration energy and high-temperature heat treatment for the purpose of improving the quality of high-dose SI M0X substrates has been proposed. (JP-A-1-17444). This is because the required dose is divided into multiple doses and implanted, reducing the damage introduced to the substrate during each implant and performing a high-temperature heat treatment each time. The purpose is to reduce defects such as threading dislocations in the finally obtained SOI layer by recovery. In this method, the oxygen ion implantation amount conventionally used for manufacturing high-dose SIM0X substrates is divided and implanted, and the thickness of the finally obtained BOX layer does not change. It has also been pointed out that the use of this method causes significant undulations in the BOX layer formed in the intermediate stage, and the effect of this method degrades the interface flatness of the finally obtained BOX layer. .

 As a method to avoid this problem, the BOX layer and SO formed after the first heat treatment can be formed by using two implantations and using a lower acceleration energy in the second implantation than in the first implantation. A proposal has been made for the purpose of improving the flatness of the interface by injecting oxygen ions mainly into the interface of the I layer (JP-A-4-249323). However, this is also an invention aimed at improving the quality of the high-dose SIM0X substrate, and the oxygen ion implantation amount conventionally used for manufacturing the high-dose SIM0X substrate is divided and injected as in the previous example. Therefore, there is no change in the thickness of the finally obtained BOX layer. Furthermore, since the second oxygen ion implantation is performed above the once formed BOX layer, the finally obtained SOI layer tends to be thinner. Therefore, this technology is not suitable for increasing the thickness of the BOX layer while securing the thickness of the SOI layer.

An object of the present invention is to provide a technology that enables a buried oxide layer of a SIM0X substrate to be thickened without these difficulties. And In particular, in the case of SIM0X substrates fabricated using a low dose region as the oxygen ion implantation amount, the BOX layer thickness can be increased with good quality, enabling high performance LSIs. It is intended to provide a high quality SOI substrate and a method of manufacturing the same. Disclosure of the invention

 In the SIM0X method, in which oxygen ions are implanted into a single-crystal silicon substrate and then subjected to high-temperature heat treatment to form a S0I structure, a BOX layer is formed by high-temperature heat treatment, and then the BOX layer is When the enzyme ion is implanted again at a deeper position and the high-temperature heat treatment is performed again, the thickness and crystallinity of the SOI layer are maintained, and the generation of silicon islands in the BOX layer is suppressed. We have newly found that it is possible to increase the thickness of the BOX layer. That is, the present invention relates to a method for manufacturing an SOI substrate for solving the above-mentioned problems, and further relates to an SOI substrate manufactured by using those techniques, and is based on the following means.

 In other words, oxygen ions are implanted into a silicon substrate and then subjected to a high-temperature heat treatment. After the formation of the B0 X layer, oxygen ion implantation is further performed, and the maximum position of the implanted oxygen distribution is located below the interface between the BOX layer and the substrate below it. It is characterized by repeating the high temperature heat treatment.

 Further, in the above-described method for manufacturing a SIMOX substrate, the dose of the oxygen ion implantation to be further performed does not exceed the total dose of the oxygen ion implantation performed up to that time.

In the method for manufacturing a SIM0X substrate, the acceleration energy used for oxygen ion implantation and the acceleration energy used for oxygen ion implantation may be further used. It is characterized by different acceleration energies.

 Further, in the above-described method for manufacturing a SIMOX substrate, a part of the surface of the already formed SOI layer is partially removed before further performing oxygen ion implantation.

 Further, the method for removing the surface of the S0I layer is etching using a reactive substance.

 Alternatively, the method is characterized in that the method of removing the surface of the SOI layer is a method of forming an oxide layer by oxidizing the substrate surface and then removing the oxide layer.

 Alternatively, the method for removing the surface of the S0I layer is surface polishing.

 In the method for manufacturing a SIMOX substrate, it is preferable that the number of repetitions of the oxygen ion implantation and the high-temperature heat treatment is two.

 In any of the above-described methods for manufacturing a SIM0X substrate, an oxide layer is formed on the silicon substrate surface before oxygen ion implantation, and the oxide layer is removed after oxygen ion implantation or high-temperature heat treatment. Preferably.

In the method for manufacturing a SIMOX substrate, the oxygen ion implantation is further performed under the conditions of an acceleration energy of 150 keV or more and 250 keV or less and a dose of 2 × 10 ¹⁷ cnT ² or more and 6 × 10 ¹⁷ cm— ² or less. Implantation is performed under the conditions that the acceleration energy is 150 keV or more and 250 keV or less, the dose is 0.1 X 10 ¹⁷ cnf ² or more and 6 X 10 ¹⁷ cm- ² or less, and the total removal depth of the silicon surface is 20 nm or more and 300 nm or less. preferable.

Also, a SIMOX substrate manufactured by any one of the above methods, wherein the thickness of the SOI layer of the SIM0X substrate is 10 nm or more and 400 nm or less, and the thickness of the BOX layer is 60 nm or more and 250 nm or less. SIM0X board. According to the present invention, oxygen ion implantation and high-temperature heat treatment A low-dose SIMOX-like BOX layer is produced. Therefore, when the implanted oxygen from the oxygen ion implantation that is further performed is precipitated in the subsequent high-temperature heat treatment, the oxygen is absorbed by the BOX layer because the BOX layer already exists. More stable deposition is achieved, and as a result, a single BOX layer can be obtained stably. In the present invention, it is also possible to reduce the pinhole defect density in the BOX layer at the same time as increasing the thickness of the BOX layer. BRIEF DESCRIPTION OF THE FIGURES

 Fig. 1 is a diagram showing the manufacturing steps 1) and 2) of a conventional SIMOX substrate, the schematic cross section of the silicon substrate in each step, and the oxygen concentration distribution.

 FIG. 2 is a diagram showing a manufacturing process 3), 4) of a SIMOX substrate according to the first embodiment of the present invention, a schematic cross section of a silicon substrate in each process, and an oxygen concentration distribution thereof.

 FIG. 3 is a diagram showing a manufacturing process 3), 4), 5) of a SIMOX substrate according to the second embodiment of the present invention, a schematic cross section of the silicon substrate in each process, and an oxygen concentration distribution thereof. .

 FIG. 4 is a schematic cross-sectional view of a silicon substrate in each of the steps 3), 4), 5), and 6) of the manufacturing process of the SIMOX substrate according to the third embodiment of the present invention, and the oxygen concentration distribution thereof. FIG.

 FIG. 5 is a graph comparing the pinhole defect densities of the BOX layer in the first to third embodiments of the present invention, the conventional example, and the comparative example.

 FIG. 6 is a graph comparing the dielectric breakdown voltage of the BOX layer in the first to third embodiments of the present invention, the conventional example, and the comparative example.

 FIG. 7 shows the third embodiment of the present invention, a conventional example, and a comparative example.

4 is a graph comparing the defect densities of the S0 I layer. BEST MODE FOR CARRYING OUT THE INVENTION

 A preferred embodiment according to the present invention will be described with reference to the schematic sectional views of FIGS.

The first half of the process of manufacturing a SIM0X substrate according to the embodiment of the present invention uses the process of manufacturing a SIM0X substrate according to the conventional technique shown in FIG. In the process shown in Fig. 1, 1) a single-crystal silicon substrate 1 is mounted on an ion implanter, and oxygen ions are predetermined on the surface while heating the substrate to maintain its crystallinity. The oxygen ion implantation region 2 'is formed by performing the implantation up to the dose amount. Subsequently, the substrate is removed from the ion implanter and 2) subjected to a high-temperature heat treatment in a heat treatment furnace to form a SIM0X structure having an S0I layer 3 'and a BOX layer 4'. As the predetermined dose, for example, when forming a SIM0X substrate in a low dose region using an acceleration voltage of oxygen ion implantation of 150 kV or more and 250 kV or less, a BOX layer of good quality is formed. to obtain the, ² Xl0 ^{1 7} cm- 2 or more 6 X 10 ¹⁷ cm- ² it is desirable to use the following dose. In the description of this specification, the above-described oxygen ion implantation and high-temperature heat treatment are referred to as first oxygen ion implantation and first high-temperature heat treatment, respectively.

In the first embodiment of the present invention shown in FIG. 2, after the step of FIG. 1 is completed, the substrate is mounted on the ion implanter again. 3) Oxygen ion implantation is performed. The oxygen ion implantation region 2 is formed by using an accelerating voltage that is arranged below the BOX layer 4 ′ in which the peak has already been formed. Then, the substrate is removed from the ion implanter and 4) high-temperature heat treatment is performed in a heat treatment furnace to form a SIM0X structure having the S0I layer 3 and the B0X layer 4. In the description of this specification, the above-described oxygen ion implantation and high-temperature heat treatment are referred to as a second oxygen ion implantation and a second high-temperature heat treatment, respectively. According to the method of FIG. 2, the oxygen ions implanted for the second time are aggregated from below on the already formed BOX layer 4 ′ in the second high-temperature heat treatment performed thereafter. At this time, in order to realize more stable coagulation, it is desirable that the dose of oxygen ion injected second time does not exceed the dose of oxygen ion ion of the first time. In this case, during the second high-temperature heat treatment, the oxygen ions implanted the second time do not precipitate independently but preferentially aggregate in the already formed BOX layer 4 ′. Will advance. In addition, since the precipitation process from the second oxygen ion implantation to the high-temperature heat treatment proceeds with almost no effect on the upper interface of the BOX layer 4 ', the thickness uniformity of the SOI layer is maintained as a result. The BOX layer 4 can be made thicker as it is.

 Also, as is well known, the damage caused by the implanted ions to the implanted material increases as the ions lose energy in the implanted material and slow down. Therefore, the degree of damage that the ions cause to the implanted material increases near the position where the ions stopped. According to the method of FIG. 2, the damage that occurs in the substrate during the second ion implantation can be concentrated inside or below the BOX layer 4 ′ formed by the first high-temperature heat treatment. Therefore, it is possible to suppress the occurrence of new damage due to the second implantation of oxygen ions into the already formed S0 I layer 3 ′, and as a result, the S0 formed after the second high-temperature heat treatment Generation of defects such as threading dislocations in the I layer 3 can be suppressed.

In the second embodiment of the present invention shown in FIG. 3, after the step of FIG. 1 is completed, 3) the S0 I layer is thinned by removing a part of the surface of the S0 I layer 3 '. . After that, the substrate was mounted on the ion implanter again. 4) Oxygen ion implantation was performed in the same manner as in FIG. This is performed using an accelerating voltage that is located below the BOX layer 4 'where the peak has already been formed. After that, the substrate is taken out of the ion implanter and subjected to a high-temperature heat treatment in a heat treatment furnace to form a SIM0X structure having a SOI layer 3 and a BOX layer 4.

 According to the method of FIG. 3, compared to the method of FIG. 2, the oxygen ion implantation to the desired position can be performed without changing the accelerating voltage used for the second oxygen ion implantation from the value used for the first implantation. Becomes possible. Therefore, within the performance range of the ion implanter to be used, the degree of freedom of the combination of the accelerating voltage in the two implantations is increased. Becomes possible. In addition, the load associated with changing the conditions of the ion injector is reduced. As a method for removing a part of the SOI layer surface before the second ion implantation, a method such as reactive ion etching, etching using a mixed solution of hydrofluoric-nitric acid, and mechanical polishing can be applied.

 In the third embodiment of the present invention shown in FIG. 4, after the step of FIG. 1 is completed, 3) a thermal oxide layer 5 is formed on the surface of the S0I layer 3 ', and 4) Remove the layer. As a method for removing the oxide layer, a solvent or the like that dissolves only the oxide layer can be used. Subsequently, 5) ion implantation as in FIG. 2 and 6) heat treatment are performed to form a SIM0X structure including the SOI layer 3 and the BOX layer 4. Also in this method, the same effect as that described in the second embodiment can be expected.

In the third embodiment of the present invention shown in FIGS. 2 to 4, an oxide layer was previously formed on the surface of the silicon substrate before the first oxygen ion implantation, and the first The oxide layer may be removed using a solvent as described above after oxygen ion implantation or after a high-temperature heat treatment performed immediately thereafter. In this case, the oxide layer formed on the surface must be removed by sputtering during oxygen ion implantation. It is more desirable that the thickness be 30 nm or more. On the other hand, in order to obtain the S0I layer after the high-temperature heat treatment, the thickness of the surface oxide layer must be suppressed to about 400 nm at the maximum.

Further, in the first to third embodiments of the present invention shown in FIGS. 2 to 4, oxygen ion implantation is performed twice in total, but as long as the S0I layer does not disappear, S0I The partial removal of the layer, the subsequent oxygen ion implantation, and the high-temperature heat treatment may be repeatedly performed. As described above, when the acceleration voltage of oxygen ion implantation is 150 kV or more and 250 kV or less and the dose is 2 × 10 ¹⁷ cm— ² or more and 6 × 10 ¹⁷ cm— ² or less, S0I The total removal depth of the layer surface or the silicon single crystal surface is desirably 20 nm or more in order to obtain the effect of the present invention, and 300 nm or less in order not to lose the SOI layer. In this case, the thickness of the finally obtained S0I layer is limited to about 400 nm, and the thickness below that is adjusted by adjusting the process conditions so that the S0I layer itself does not disappear. Can be formed.

In addition, in the first to third embodiments of the present invention shown in FIGS. 2 to 4, the thickness of the BOX layer is increased to improve the quality of the BOX layer, such as pinhole defects and dielectric strength. Is also improved. The degree of improvement increases as the total dose in the second and subsequent oxygen ion implantations increases.However, in order to obtain a clear improvement in the quality of these BOX layers, the dose of oxygen ions in the second and subsequent injections must be increased. It is desirable that the total amount be at least 0.1 × 10 ¹⁷ cm— ² or more, more preferably 0.5 × 10 ¹⁷ cm— ² or more.

Further, as for the apparatus for performing oxygen ion implantation in the present invention, it is sufficient that oxygen ions can be implanted from the surface of a silicon wafer after acceleration by applying a voltage to the oxygen ions. The method is not particularly limited. In addition, the conditions for the first oxygen ion implantation in the production of the SI MOX substrate according to the present invention have already been described in the low dose region, but are not particularly limited thereto. The so-called medium-dose region or high-dose region condition may be used.However, from the viewpoint of improving the BOX quality such as thicker BOX layer, If the present invention is applied when conditions are used, a greater effect can be expected. Further, each of the first oxygen ion implantation and the second and subsequent oxygen ion implantations may be performed in plural times. From the viewpoint of reducing crystal defects in the SOI layer, it is desirable that the substrate temperature during the first ion implantation be at least about 500 ° C to 600 ° C.

 The apparatus for performing the high-temperature heat treatment is not particularly limited as long as the heat treatment at a desired temperature can be performed for a desired time. As a device that is preferably used, a high-temperature heat treatment furnace is typically mentioned, but a lamp annealing furnace can be used if the performance such as a processing temperature and a processing time is satisfied. Conditions other than the processing temperature and the processing time in the heat treatment furnace, such as the insertion temperature, the heating rate, and the cooling rate, are not particularly limited, and the heating and cooling may be performed in multiple stages.

Regarding high-temperature heat treatment conditions, in order to remove damage caused by implantation and obtain a high-quality SOI structure, it is desirable to use a temperature of 1300 ° C or higher but not exceeding the melting point of silicon, but it is particularly limited to this. It is not something. The atmosphere is preferably a non-oxidizing atmosphere using an inert gas or an atmosphere to which a small amount of oxygen has been added for damage removal, but is not particularly limited to this, and may be an oxidizing atmosphere. As the inert gas, argon, nitrogen or the like is typically used, but it is not particularly limited to these. A high-temperature oxidation treatment may be performed subsequent to the high-temperature heat treatment. Example

 An embodiment according to the present invention will be described below with reference to the schematic sectional views of FIGS.

According to the process shown in FIG. 1, oxygen ions were implanted into the surface of the P-type (100) silicon substrate at an acceleration voltage of 180 kV to a dose of 4 × ^{10 17} cm− ² . The substrate temperature during implantation was set at 600 ° C from the viewpoint of maintaining crystallinity. Subsequently, the substrate was taken out of the ion implanter and subjected to a heat treatment at a temperature of 1300 ° C. or more for 6 hours in a heat treatment furnace to form a SIM0X structure. The heat treatment was performed in an atmosphere in which 1% or less of oxygen was mixed with argon. When the structure of the substrate taken out of the furnace was evaluated by spectroscopic measurement, the thickness of the SOI layer was about 340 nm and the thickness of the BOX layer was 85 nm. In the first example according to the first embodiment of the present invention shown in FIG. 2, after the step of FIG. 1 is completed, the substrate is mounted on the ion implanter again, and oxygen ions are accelerated to an acceleration voltage of 210 kV. The injection was performed to an injection amount of 2 × ^{10 17} cm− ² . The substrate temperature at the time of implantation is the same as in the first implantation,

600 ° C was used. Thereafter, the substrate was taken out of the ion implanter and heat-treated in a heat treatment furnace at a temperature of 1300 ° C or higher for 6 hours in an atmosphere in which 1% or less oxygen was added to argon. After heat treatment, the sample taken out of the furnace was evaluated by spectroscopic ellipsometry in the same manner as described above. The thickness of the SOI layer was about 280 nm and the thickness of the BOX layer was 130 nm.

In the second embodiment according to the second embodiment of the present invention shown in FIG. 3, after the step of FIG. 1 is completed, the surface of the SOI layer is brought to a depth of about 120 nm using a mixed solution of hydrofluoric and nitric acid. Etching was performed to reduce the thickness of the SOI layer to about 200 nm. Thereafter, the substrate was mounted on the ion implanter again, and oxygen ions were implanted at an acceleration voltage of 190 kV to an injection amount of 2 × ^{10 17} cm− ² . The substrate temperature at the time of implantation was 600 ° C as in the first implantation. . Thereafter, the substrate was taken out of the ion implanter and heat-treated in a heat treatment furnace at a temperature of 1300 ° C or more for 6 hours in an atmosphere in which 1% or less oxygen was added to argon. After the heat treatment, the substrate removed from the furnace was evaluated by spectroscopic ellipsometry in the same manner as described above. The thickness of the SOI layer was about 160 nm, and the thickness of the BOX layer was 130 nm.

 In the third example according to the third embodiment of the present invention shown in FIG. 4, after the step of FIG. 1 is completed, a thermal oxide layer having a thickness of about 270 nm is formed on the SOI layer surface at 1000 ° C. After forming at the above temperature, the oxide layer was removed using a hydrofluoric acid solution. As a result, a thickness of about 220 nm was left as the SOI layer. Thereafter, ion implantation and heat treatment were performed under the same conditions as in the second embodiment. The thickness of each layer finally obtained was about 160 nm for the SOI layer and about 130 nm for the BOX layer.

The quality of the BOX layer was compared and evaluated for the obtained sample substrates. In the evaluation, in addition to the samples of the above three examples, the conventional example manufactured in the process of FIG. 1 and the oxygen ion implantation in the process of FIG. A comparative example performed at an injection amount of ¹⁷ cm- ² was also evaluated.

Pinhole defects in the BOX layer were evaluated by copper electrodeposition. The sample was immersed in a plating solution containing copper ions so that only the front surface of the substrate was in contact, the back surface of the substrate was brought into contact with an electric cathode, and an electric anode was placed in the plating solution. Then, by applying a low voltage of about 10 V between the two electrodes, which does not destroy the BOX layer itself, copper deposits are generated on the substrate surface immediately above the pinhole in the BOX layer. The pinhole density in the BOX layer was evaluated by counting the number. FIG. 5 shows the pinhole densities of the samples of the conventional example, the first embodiment, the second embodiment, the third embodiment, and the comparative example. Compared to the conventional example, the pinhole density in the first embodiment, the second embodiment, the third embodiment, and the comparative example is lower. The number was reduced to almost 1/5, and it was found that the number of pinholes decreased with the increase in the total amount of oxygen injected.

Subsequently, the withstand voltage of the BOX layer of each sample was evaluated. Dividing the S0 I layer Ri by the re lithography and etching an area of l mm ^2, the A1 electrode was formed Ri by the vacuum deposition on the surface. An Au film was formed on the back surface of the substrate by vacuum evaporation as the other electrode. An electric field was applied to the BOX layer by applying a voltage between the A1 electrode and the Au electrode on the back of the substrate, and the electric current flowing at that time was measured to evaluate the breakdown electric field of the BOX layer. The electric field value was calculated by dividing the voltage applied between both electrodes by the BOX layer thickness.

 Fig. 6 shows the breakdown electric field strength of the BOX layer in the conventional example, the first example, the second example, the third example, and the comparative example. It can be seen that the breakdown electric field strength of the BOX layer is improved in the first embodiment, the second embodiment, and the third embodiment as compared with the conventional example. On the other hand, in the comparative example manufactured with the same dose as that of the third example, it was found that the withstand voltage characteristics of the BOX layer were lower than the conventional example. This is considered to be due to the fact that simply increasing the dose of oxygen ions increased the number of silicon islands in the BOX layer, thereby lowering the dielectric strength.

Figure 7 shows the defect density of the S0I layer of each sample evaluated by the etch pit. Compared to the conventional example, the defect density is suppressed to the same level in the first embodiment, the second embodiment, and the third embodiment despite the addition of ion implantation. You can see that. On the other hand, in the comparative example in which the same amount of oxygen ions as in the first embodiment, the second embodiment, and the third embodiment was injected at one time, the defect density of the SOI layer increased by two orders of magnitude. It is shown that the amount of damage increases with an increase in the amount of implanted ions. This result indicates that in the first embodiment, the second embodiment, and the third embodiment, the second oxygen ion implantation is performed in the first heat treatment. Since most of the damage generated at this time is introduced inside or below the BOX layer as a result of being applied to the lower side of the formed BOX layer, defects in the SOI layer finally obtained as a result of being introduced into or below the BOX layer It can be understood that the effect of generation has been reduced.

 Summarizing the above results, in the first embodiment, the second embodiment, and the third embodiment using the present invention, the thickness of the BOX layer is increased as compared with the conventional example, and the BOX layer is thickened. It can be seen that while pinhole reduction and dielectric strength improvement have been achieved, the increase in defects in the SOI layer has been suppressed despite the increased oxygen ion implantation. Industrial applicability

 As described above, according to the present invention, in the manufacture of the SI M0X substrate, additional oxygen implantation is performed on the SI M0X substrate manufactured by the conventional technology, and the maximum position of the implanted oxygen distribution is changed. It is manufactured by the conventional method by applying it so that it is located below the interface between the BOX layer formed up to that point and the substrate below it, and then performing high-temperature heat treatment. Compared to SI M0X substrates, it is possible to manufacture thicker BOX layers with higher quality.

Claims

The scope of the claims 1. In the method of manufacturing a SIMOX substrate that forms a buried oxide layer and a surface silicon layer by implanting oxygen ions into a silicon substrate and then performing high-temperature heat treatment, the high-temperature heat treatment is performed after oxygen ion implantation. After the buried oxide layer is formed by performing the above, oxygen ion implantation is further performed, and the maximum position of the implanted oxygen distribution is located below the interface between the buried oxide layer formed up to that point and the substrate below it. A method for manufacturing a SIM0X substrate, characterized in that a high-temperature heat treatment is performed after that.  2. Injection of oxygen ions into the silicon substrate followed by high-temperature heat treatment, the high-temperature heat treatment is performed after the oxygen ions are implanted in the method of manufacturing the SIMOX substrate that forms the buried oxide layer and the surface silicon layer. After the formation of the buried oxide layer, the oxygen ion implantation is further performed so that the dose of the oxygen ion implantation does not exceed the sum of the doses of the oxygen ion implantation performed up to that time. The maximum position of the S is located below the interface between the buried oxide layer formed up to that point and the substrate under the buried oxide layer, followed by high-temperature heat treatment. IM0X Substrate manufacturing method. 3. By implanting oxygen ions into the silicon substrate and then subjecting it to high-temperature heat treatment, the high-temperature heat treatment is performed after the oxygen ions are implanted in the method of manufacturing a SIMOX substrate that forms a buried oxide layer and a surface silicon layer. After the buried oxide layer is formed by performing the oxygen ion implantation, the acceleration energy used for the previous oxygen ion implantation is made different from the acceleration energy used for the oxygen ion implantation, so that the maximum distribution of the implanted oxygen is increased. The position is lower than the interface between the buried oxide layer formed up to that point and the substrate below, and then high-temperature heat treatment is performed. A method for manufacturing a SIM0X substrate, the method comprising:  4. Oxygen ions are implanted into the silicon substrate and then subjected to a high-temperature heat treatment to form a buried oxide layer and a surface silicon layer. After the buried oxide layer is formed by performing the high-temperature heat treatment, oxygen ion implantation is further performed so that the dose of the oxygen ion implantation does not exceed the total dose of the oxygen ion implantation performed up to that time. At the same time, the acceleration energy used for the previous ion implantation is different from the acceleration energy used for this oxygen ion implantation, so that the maximum position of the implanted oxygen distribution and the lower part of the buried oxide layer have been formed. A method for manufacturing a SIM0X substrate, characterized in that the substrate is placed below the interface with the substrate, and then a high-temperature heat treatment is performed.  5. By implanting oxygen ions into the silicon substrate and then subjecting the silicon substrate to high-temperature heat treatment, the method of manufacturing the SIMOX substrate forming the buried oxide layer and the surface silicon layer has a high temperature after oxygen ion implantation. After the heat treatment to form the buried oxide layer, the surface of the already formed surface silicon layer is partially removed, and oxygen ion implantation is performed, and the maximum position of the implanted oxygen distribution has been formed up to that point. A method for producing a SIM0X substrate, comprising: placing the buried oxide layer below an interface between the buried oxide layer and a substrate below the buried oxide layer; and then performing a high-temperature heat treatment. 6. Oxygen ions are implanted into the silicon substrate and then subjected to a high-temperature heat treatment. In the method of manufacturing a SIMOX substrate that forms a buried oxide layer and a surface silicon layer, a high-temperature heat treatment is performed after the oxygen ions are implanted. After the formation of the buried oxide layer, the surface of the already formed surface silicon layer is partially removed, oxygen ions are further implanted, and the oxygen ion implantation dose is reduced to Do not exceed the total ion implantation dose, and make sure that the maximum position of the implanted oxygen distribution is A method for manufacturing a SI M0X substrate, wherein the method is performed so that the buried oxide layer is formed below an interface between the buried oxide layer and a substrate therebelow, and then a high-temperature heat treatment is performed.  7. Oxygen ions are implanted into the silicon substrate and then subjected to a high-temperature heat treatment, so that the buried oxide layer and the surface silicon layer are formed. After performing the heat treatment to form the buried oxide layer, the surface of the already formed surface silicon layer is partially removed, and oxygen ion implantation is performed using the acceleration energy used for the previous oxygen ion implantation and the oxygen energy. The acceleration energy used for ion implantation should be different, and the maximum position of the implanted oxygen distribution should be located below the interface between the buried oxide layer formed up to then and the substrate below it. And then performing a high-temperature heat treatment.  8. By implanting oxygen ions into the silicon substrate and then subjecting it to high-temperature heat treatment, high-temperature heat treatment is performed after oxygen ion implantation in the method of manufacturing a SIMOX substrate that forms a buried oxide layer and a surface silicon layer. After the buried oxide layer is formed, a part of the surface of the already formed surface silicon layer is removed, and oxygen ion implantation is further performed. The maximum position of the implanted oxygen distribution should be maintained so that the total dose of the implant does not exceed the acceleration energy used for the previous ion implantation and the acceleration energy used for this oxygen ion implantation. The heat treatment is performed so that the buried oxide layer is formed below the interface between the buried oxide layer and the substrate under the buried oxide layer. SIM0X Substrate manufacturing method. 9. The method of removing the surface silicon layer surface is to remove by etching using a reactive substance or to oxidize silicon on the substrate surface. The method according to claim 5, wherein the oxide film is formed by removing the oxide film, or the surface is polished. Substrate manufacturing method.  10. The method for removing the surface silicon layer surface is to remove the oxide film by etching using a reactive substance or by oxidizing silicon on the substrate surface to form an oxide film. 7. The method for producing a SIM0X substrate according to claim 6, wherein the method is any one of the following methods:  11. The method for removing the surface silicon layer surface is to remove by etching using a reactive substance, or to oxidize silicon on the substrate surface to form an oxide film, and then remove the oxide film. 8. The method for producing a SIM0X substrate according to claim 7, wherein the method is any one of the following methods.  12. The method for removing the surface silicon layer surface is to remove by etching using a reactive substance or to oxidize silicon on the substrate surface to form an oxide film and then remove the oxide film. 9. The method for producing a SIM0X substrate according to claim 8, wherein the method is any one of: a method of removing by surface polishing.  13. A SIM0X substrate manufactured by the manufacturing method according to any one of claims 1 to 12, wherein a thickness of a surface silicon layer of the SIM0X substrate is 10 nm. A SIM0X substrate having a thickness of 400 nm or less and a buried oxide layer of 60 nm or more and 250 nm or less.